FIELD OF THE INVENTION
The subject method of dynamically generating navigation route data is generally directed to a system for making available a route to be followed by a host vehicle. More specifically, the subject method is one wherein the information sufficient to unambiguously define a given route, or path of travel, is pre-stored, then subsequently retrieved and processed to geometrically render the route when needed.
In virtually all vehicle navigation system applications, a distinct path to be followed by the vehicle is defined by a series of way points expressed in appropriate coordinates of a given reference system, or as a string of vectors extending between such coordinates. The vehicle attempts, either in automatically or manually guided manner, to travel successively through each way point, beginning with the first and ending with the last. Such way point-defined paths are heavily utilized in air traffic control applications, for instance, to direct aircraft through airport/runway arrival/approach and departure routes.
While they are typically defined quite distinctly, routes to be flown may invariably be categorized into one or more sets delineating generally identifiable path types. A particular route path, for instance, may be of such type as: line segment, S-turn maneuver, path extension, holding pattern, or the like. Despite sharing geometric attributes, however, distinct route paths of the same general type normally contain significantly different way point coordinates, as each is defined in a manner specific to a particular locale. Even within a common locale, route paths of the same general type may differ significantly in their constituent way point coordinates, where they are to actually be traveled by a host aircraft at different dates or times.
Consequently, aircraft vehicles typically have pre-stored within their onboard flight management system (FMS) or area navigation (RNAV) computers complete sets of way points peculiar to each of its origination and destination airports/runways. The pre-storing of such way point coordinate sets may be effected on the ground well before take-off, or even uploaded during flight through a suitable communications link, if available. Regardless, the entire set of way points for each distinct path that the given aircraft vehicle may be required to fly at the given locales is fully pre-stored and made accessible in the vehicle's FMS a priori.
The resulting mass of data to be stored and managed is quite excessive. Not surprisingly, a worldwide base of such data may be maintained only at enormous costs. The massive set of data consumes an inordinate share of hardware, software, and labor resources which in many applications may already be all too scarce in availability. In some cases, as in aircraft built before, say, 1990, the resources necessary to store the entire set of data for even one trip are typically not available.
The mass of data, moreover, serves unavoidably to inhibit and undermine operational factors that ultimately bear heavily upon both safety and cost concerns. The cumbersome amount of data needed to unambiguously define particular approach paths, for example, makes rather daunting the task of replacing an existing path definition with an updated, corrected, or otherwise modified path definition. This is especially so where the task is to be attempted during flight--over an available data exchange link established with a remote site or vehicle. The difficulty of the task is compounded in such cases by the need to transfer the necessary data in a sufficiently short time through radio wave traffic that, particularly in the vicinity of airports, may be extremely heavy.
It may not be possible in a given case, then, to insure a complete transfer of what may be the most critical path modifications or updates - the most recent ones. Consequently, an approaching aircraft may be left without the data to effect the late stage modifications required by factors like shifting weather conditions, equipment failure, or any of numerous other exigencies likely to affect traffic. Such inability to adapt to changing circumstances yield significant inefficiencies in the traffic flow in and through a given area.
Closely related to the lack of adaptability prevailing in existing systems is the difficulty of maintaining system integrity. In applications like air traffic control, effectively maintaining overall system integrity rests heavily upon effectively maintaining both data integrity and intent integrity. In terms of data integrity, the excessive amount of data necessarily maintained in a given aircraft's navigation computer and/or exchanged through available communications links introduces a proportionately high risk of unavoidable random error. Each additional electronic data element stored, received, or otherwise handled, for example, introduces an additional source of potential data corruption. Moreover, the weight of the workload in manipulating such excessive amounts of data not only strains system resources, it strains the personal resources of a pilot or other human operator. Of pertinent note in this regard is that the world's aircraft navigation database is currently updated and replaced every 28 days.
Overseeing and effecting the exchange of path, or route, way point information with an ATC ground station, for example, is rendered highly labor-intensive by the excessive amount of data involved. This unduly heightens the system's exposure to human error in the form of the operator either being too preoccupied with other onboard tasks to pay adequate attention to the given system task or, conversely, too preoccupied with the given system task to pay adequate attention to the other necessary onboard tasks. Directly or indirectly, a compromise of data integrity would invariably result in such cases.
In addition to data integrity, it is important that intent integrity be maintained. That is, the particular path that the given vehicle itself `intends` to follow and the particular path that the ground-based control station system `intends,` or expects, the vehicle to follow must be one and the same. Without the adaptability in existing systems to afford the rapid and reliable exchange of path information between a vehicle and a traffic controlling ground station, maintaining this intent integrity presents a significant challenge. If the uniquely-prescribed way point definitions for the set of available paths at a given airport have been at all modified since their last definition or update for charting purposes, a vehicle may very well be operating with an outdated version of one or more such way point path definitions, and may therefore unwittingly deviate from the control station-designated path.
The situation may be aggravated where, as at many airports, certain of its paths are defined in terms of local coordinates relative to locally-positioned navigational aids such as VHF omnidirectional radial range (VOR) devices, rather than in terms of absolute coordinates. Such lack of reference standardization only adds to the potential for confusion between the aircraft and the ground station.
Not surprisingly, there continues to be an effort by some in the art to limit the number of different paths/routes available for approach to and departure from each airport. This, however, would further constrict the adaptability of a system already plagued by the absence of sufficient adaptability.
Even where available system resources and applicable conditions would permit the required exchange of data between a vehicle and the ground station to check integrity, a meaningful check of way point-defined paths would yet require a great number of data elements to be exchanged. Thus loaded down by excessive data content, the vehicle's onboard system may be left without the adequate availability of resources to update the aircraft's intended path or effect other remedial action, even if a disparity between the aircraft-intended and the ground base-expected paths were correctly detected.
Another factor bearing on navigation system safety and cost concerns is that of standardization. As briefly alluded to in preceding paragraphs, the prevalent approach of defining each distinct path by the entire set of its constituent way points is hardly conducive to universal standardization. While the additional impediments to standardization due to expression of way points relative to localized navigational aid devices may in certain cases be substantially mitigated by the prevailing use of Global Positioning System (GPS) receivers on vehicles; the need to maintain a cumbersome definition for each and every distinct flight path would nevertheless limit the effectiveness of the standardization effort. As a practical matter, the gains to be had from a standardized reference for expressing and exchanging flight path data would ineffectually offset the persistent burden of maintaining each flight path prestored in a given aircraft's navigation computer, particularly the burden of maintaining each in an up-to-date manner. Failure to so maintain the path data base would immediately invoke the problems discussed in preceding paragraphs.
There is, therefore, a need for a method or system for providing vehicle navigation path, or route, data that overcomes the efficiency, adaptability, integrity, and standardization problems encountered by existing methods and systems.